The State Analysis And Operation Optimization Research Of Indirect Air Cooling System With Compound Refrigeration Cycle

Coal is the primary energy used for electricity generation in our country, mainly distributed in Northeast, Northern and Northwest regions. However, the water resources of these regions are extreme shortages. In order to solve the geographic contradiction of primary energy and water resources for steam power cycle power plant dominated by coal, air cooling technology is widely used. Due to the change of the amplitude and frequency of air temperature and volume are difficult to forecast accurately, it is difficult for the air cooling system to maintain for a long time worked under design conditions, thus reducing its economic operation. In view of the defects, an air cooled system with compound refrigeration cycle (CRC-IAC) is presented for the steam cycle power plants.According to the application problem of the CRC-IAC, this paper mainly carried out the following work:In this paper, based on the coupling correlation principle between steam power cycle and composite refrigeration cycle and the work process of refrigeration cycle and Rankine cycle, by three rounds of comparing selection in environmental performance, parameters matching and power capability, ammonia is became the preferred medium due to its excellent refrigeration performance, performance ability and environmental performance.A complete analysis and calculation methods is presented to quantitatively evaluate the influence of significant, high frequency and randomness change of environmental temperatures on the operation efficiency. By the contrastive analysis, the quantitative association between thermal efficiency transition temperature of CRC-IAC plant and environmental temperature at high temperature period was analyzed. The annual cumulative output power (ACOP) of CRC-IAC plant was used as the target variables, the design exhaust pressure is optimal designed. Then a definition and calculation method of site sensitivity coefficient (SSC) is presented, and the influence of environment temperature of plant site on the thermal efficiency is revealed.A mathematical model for the calculation of off-design operation of the CRC-IAC system was formed based on the energy transformation and transfer processes mechanism in this paper. They include an off-design calculation model of steam turbine exhaust pressure for refrigerating cycle during high ambient dry-bulb temperature period. And the calculation model quantitatively reveal that compressor power, ambient dry-bulb temperature, face velocity of air cooling radiator and exhaust thermal load are the main factors affecting the exhaust pressure. The expander power is selected as the dominant variable for the off-design calculation model of inverse refrigeration cycle during low ambient dry-bulb temperature period, and the model analyses show that the main influence factors include the exhaust pressure of turbine, superheat degree of cooling medium, ambient dry-bulb temperature, face velocity of air cooling radiator and exhaust thermal load.A real-time algorithm of best exhaust vacuum and years of accumulated generating capacity is presented based on the best vacuum characteristics of CRC-IAC system during high and low ambient dry-bulb temperature period. And then the life cycle emissions and life cycle cost are comparative evaluated between CRC-IAC plant and the direct air cooling plant with the same parameters and site by the method of life cycle assessment. The assessment results can lay the foundation for the comprehensive assessment the economic, environmental and social benefits of CRC-IAC in future.For testing the feasibility, validity and enforceability of CRC-IAC used for cooling exhaust, we design a laboratory simulation test system of refrigeration cycle of CRC-IAC. The refrigeration cycle concatenated couples the simulated exhaust device through the condenser/evaporator. The results verify that the CRC-IAC system can signally reduce the exhaust temperature. Based on the multi-factor orthogonal experiment results, the influence rules of the environment temperature exhaust thermal load and face velocity on the condenser temperature are obtained. A novel compressed air blower (CAB) system was designed instead of high pressure desalted water to clean the ash fouling of air cool radiatore (ACR) for improve the heat transfer performance during the operation process. And the blowing evaluation indexes are proposed to quantitatively evaluate the influence of ash fouling on the exhaust condensation temperature. The field test results on an air cooled condenser of600MW plant show that:the energy conservation and water saving effect of the equipmen is obvious. With the minimum economic losses from ash fouling and CAB for the principle, a cleanliness optimization management model of ACC is proposed. The model can calculate the best cleaning cycle of CAB.